Method and apparatus for reducing vibration over the full operating range of a rotor and a host device

What is claimed is: 
     
       1. A system for minimizing vibration or stress in an apparatus including a rotor to which rotating blades are attached, said system comprising: means for calculating the effects of unit mechanical adjustments on the force and moment exerted by the rotor on a support structure of the rotor;   means for determining up to three components of force and up to three components of moment generated by the rotor;   means for detecting the angular position of a shaft of said rotor;   means for processing signals produced by said means for determining said components of force and moment and by said means for detecting the angular position of said shaft to produce Fourier coefficients of said force and moment;   means for determining, through the use of said Fourier coefficients, the optimum mechanical adjustments that will result in the minimum vibration in the support structure for the rotor;   means for prescribing adjustments to the blades in accordance with said optimum mechanical adjustments.   
     
     
       2. The system for minimizing vibration or stress in an apparatus of claim 1 wherein said means for determining components of force and moment comprises up to six accelerometers positioned to resolve up to six degrees of freedom of motion of the rotor support structure. 
     
     
       3. The system for minimizing vibration or stress in an apparatus of claim 1 wherein said means for detecting force and moment are positioned substantially at the center of mass of the rotor support structure. 
     
     
       4. The system for minimizing vibration or stress in an apparatus of claim 1 wherein a prescribed adjustment of the setting of a blade is a changing of the length of a pitch length for said blade in order to change the angel of attack of said blade. 
     
     
       5. The system for minimizing vibration or stress in an apparatus of claim 1 wherein a prescribed adjustment of the setting of a blade is a bending, in an upward or downward direction, of a tab or section on the trailing edge of said blade. 
     
     
       6. The system for minimizing vibration or stress in an apparatus of claim 1 wherein a prescribed adjustment of the setting of a blade is an adding or removing of the weights to the blade at specified locations on the blade or hub. 
     
     
       7. The system for minimizing vibration or stress in an apparatus of claim 1 wherein said means for calculating the effects of unit mechanical adjustments comprises means for obtaining a measure of the total force and moment on the rotor hub which includes the force and moment exerted by the untuned rotor on the support structure and the force and moment resulting from each type of adjustment. 
     
     
       8. The system for minimizing vibration or stress in an apparatus of claim 7 wherein said means for obtaining a measure of the total force and moment comprises means for calculating: ##EQU22## where a j  =force/moment due to unit value of the jth allowed adjustment to one blade and N=the number of allowed adjustments to one blade.   
     
     
       9. The system for minimizing vibration or stress in an apparatus of claim 8 wherein said means for determining the optimum mechanical adjustments comprises means to minimize: ##EQU23## where a n  =the Fourier coefficient of the force/moment at the nth harmonic of rotation of the rotor; A nj  =nth term is the discrete Fourier series of the jth set of allowed rotor blade adjustments (j =i, . . . , N)   F nj  =nth harmonic of the force/moment generated by the rotor due to a unit adjustment of type j.   
     
     
       10. The system for minimizing vibration or stress in an apparatus including a rotor of claim 1 further comprising: means for calculating a weighted average of the mean-square components of force and moment at a plurality of flight or operating conditions;   means for determining a set of optimum blade adjustments that minimize said weighted average.   
     
     
       11. The system for minimizing vibration or stress in an apparatus including a rotor of claim 1 wherein said means for determining the optimum mechanical adjustments comprises means for calculating: ##EQU24## α bj  =the actual optimum amount of prescribed unit blade adjustments of the jth type to the b blade A nj  =nth term in descrete Fourier series of the jth set of allowed rotor blade adjustments (j =1, . . . , N).   
     
     
       12. A method for minimizing vibration or stress in an apparatus including a rotor having a plurality of blades, said method comprising the steps of: calculating the effects of unit mechanical adjustments on the force and moment exerted by the rotor on a support structure of the rotor;   determining up to three components of force and up to three components of moment generated by the rotor;   detecting the angular position of a shaft of said rotor;   processing signals representing components of force and moment and signals representing the angular position of said shaft to produce Fourier coefficients of said force and moment;   determining the optimum mechanical adjustments of the rotor for minimizing vibration in the support structure for the rotor, said optimum adjustments being a derived from said produced Fourier coefficients of motion and from said calculated effects of unit mechanical adjustments of the blades;   adjusting to the blades in accordance with said optimium mechanical adjustments.   
     
     
       13. The method for minimizing vibration or stress in an apparatus of claim 12 wherein said step of determining the components of force and moment comprises positioning up to six accelerometers to resolve up to six degrees of freedom of motion of the support structure of the rotor. 
     
     
       14. The method for minimizing vibration or stress in an apparatus of claim 12 further comprising the step of positioning a device for determining force and moment generated by the rotor substantially at the center of mass of the rotor support structure. 
     
     
       15. The method for minimizing vibration or stress in an apparatus of claim 12 wherein said step of adjusting comprises changing the length of a pitch link for said blade in order to change the angle of attack of said blade. 
     
     
       16. The method for minimizing vibration or stress in an apparatus of claim 12 wherein said step of adjusting comprises bending, in an upward or downward direction, a tab or section on the trailing edge of said blade. 
     
     
       17. The method for minimizing vibration or stress in an apparatus of claim 12 where said step of adjusting comprises adding or removing weights to the blade at specified locations on the blade or hub. 
     
     
       18. The method for minimizing vibration or stress in an apparatus of claim 12 wherein said step of calculating the effects of unit mechanical adjustments of the blades of the rotor comprises the step of obtaining a measure of the total force and moment on the rotor which includes the force and moment exerted by the untuned rotor on the rotor support structure plus the force and moment resulting from each type of adjustment. 
     
     
       19. The method for minimizing vibration or stress in an apparatus of a claim 18 wherein said step of obtaining a measure of total force and moment comprises the step of calculating: ##EQU25## where a j  =force/moment due to unit value of jth allowed adjustment to one blade, and N=the number of allowed adjustments to one blade.   
     
     
       20. The method for minimizing vibration or stress in an apparatus of claim 19 wherein said step of determining the optimum mechanical adjustments of the blades comprises the step of minimizing: ##EQU26## where a n  =the Fourier coefficient of the force/moment at the nth harmonic of rotation of the rotor; A nj  =nth term is the discrete Fourier series of the jth set of allowed rotor blade adjustments (j =i, . . . , N)   F nj  =nth harmonic of the force/moment generated by the rotor due to a unit adjustment of type j.   
     
     
       21. The method for minimizing vibration or stress in an apparatus including a rotor of claim 20 further comprising the steps of: calculating a weighted average of the mean square components of force and moment at a plurality of flight or operating conditions;   determining a set of optimum blade adjustments that minimize said weighted average.   
     
     
       22. The method for minimizing vibration or stress in an apparatus of claim 12 wherein said step of determining the optimum mechanical adjustments comprises the step of calculating: ##EQU27## α bj  =the actual optimum amount of prescribed unit blade adjustments of the jth type to the b blade A nj  =nth term in descrete Fourier series of the jth set of allowed rotor blade adjustments (j =1, . . . , N).